Sugar cane is today transformed by the AZCUBA Enterprise Group into a series of different products (brown sugar, refined white sugar, unrefined white sugar and ecological sugar), as well as twenty derivatives.
Among the latter, electricity, alcohol, animal feed and bioproducts are significant, the Head of AZCUBA Power Generation Barbara Hernández Martínez, told Prensa Latina.
Sugar production is based on energy obtained through cogeneration – the simultaneous production of electrical and thermal energy from a single fuel – used for the clarification, filtration, evaporation and crystallization processes of sugar cane juice, she explained.
Since the sugar harvest of 2002, she added, the Cuban sugar industry has been selling increasing surplus electricity generated during the manufacturing process to the National Electrical Union. However, this has reached insufficient efficiency parameters to meet the energy needs of the country.
According to Hernández, sugar producers across the world are now abandoning the idea that sugarcane biomass (bagasse and straw) is an annoying waste product of sugar production, of low commercial value, and recognizing it as a fuel of great use in generating energy.
Biomass has been an energy source since time immemorial, and in fact was the first fuel used by human beings. Despite its ancient use, it will continue to occupy an important place in the global energy system going forward, according to a recent report by the Organization of the Petroleum Exporting Countries.
According to the Cuban official, the sugar cane industry produces the fuel it needs at very low cost, as biomass is a waste product of the milling process, thus making it both renewable and environmentally friendly.
Elaborating on the energy value of sugar cane, Hernández emphasized that the AZCUBA Bioelectrical Plants Program, once fully implemented, will have a significant impact on the diversification of agribusiness production.
The use of this raw material could see AZCUBA’s contribution to environmentally friendly energy production in the country increase fourfold, and have a positive influence on transforming the national electric system.
Currently, approximately 86% of the renewable energy produced in the country comes from sugar cane biomass.
A gradual increase of no less than 14% in the electricity generated from this biomass is expected up to 2030. Bioelectrical plants are highly efficient, not only due to the equipment used and the performance parameters, but precisely because they are cogeneration plants, releasing low pressure steam that will continue to be used in the sugar manufacturing process.
THE JESÚS RABÍ SUGAR MILL BIOELECTRICAL PLANT
The planned 20 megawatt (Mw) bioelectrical plant at the Jesús Rabí sugar mill, in the province of Matanzas (some 100 kilometers east of Havana), is one of 19 which will be installed in this sector up until 2030.
In this regard, Hernández pointed out that efforts to finance seven of these plants are underway, both through preferential buyer’s credit and other means set out in the country’s foreign investment law.
This project, the specialist explained, consists of replacing the equipment in the thermal energy area of sugar mills (steam boilers, turbine generators, water treatment equipment, transformers connected to the national electricity system, biomass storage areas) for new, energy efficient equipment.
Currently, the Jesús Rabí sugar mill has the required volume of sugar cane to process 4,500 tons of this raw material daily, however, it does not have the cogeneration capacity to ensure a 100% processing rate.
The electric power installed in this factory only supports 80% of the processing potential, fixed at 3,500 tons of cane per day.
The new bioelectrical plant will be a cogeneration plant built in an area adjacent to the mill, which will ensure that harvests during the period of construction and assembly are not negatively affected.
Once up and operating, it will consume all the bagasse and agricultural waste produced, as well as the pure steam condensate from heating and evaporation equipment and water from the sugar processing, which in turn will supply steam to the turbine generators for the sugar manufacturing process, and the electricity it requires.
The electricity surplus from the sugar manufacturing process will be sold to the Electrical Union of Cuba, the specialist added.
Hernández explained that the project consists of installing a boiler with capacity to produce 110 tons of steam per hour, which will work at a pressure of 67 bar and a temperature of 520 degrees, with no less than 85% efficiency, and use 50% moisture bagasse as fuel during harvest time.
The bagasse will be combined with ten percent of sugar cane agricultural waste during harvest time and 17% of waste at other times, mixed with the remaining sugar cane biomass from the mill itself and the remaining mills in the province of Matanzas. It will also use forest biomass (Marabou), provided by agricultural production units of the Ministry of Agriculture.
The project also aims to reduce the environmental impact of the sugar manufacturing process, with the installation of air purifiers for gases generated in the combustion of biomass.
The chosen technology will allow for continuous improvement and care of the agro ecosystem, as the residual ash from steam generation, which is high in potassium, will be applied as liquid fertilizer to the sugar cane fields.
As such, conservation and better use of water resources will result from condensing the steam extracted from the turbine.
Hernández noted that once this bioelectric plant is operational, there will be a 19% increase in raw sugar production during each harvest, as well as a fourfold increase in efficiency in the mill’s power generation.
In addition, the use of forest and sugar cane biomass will save the country an estimated $20 million dollars in fossil fuels.
The specialist revealed that works on the bioelectric plants corresponding to the 5 de Septiembre sugar mill, in the province of Cienfuegos, and the Ciro Redondo sugar mill in Ciego de Ávila, each with a capacity of 60 MW, are currently awaiting the approval of the final documents, in order for the signing of their respective financing agreements to take place.
The plant at the 5 de Septiembre mill will be built and operated through a management contract between the Cienfuegos Sugar Company and the Industrial Construction Company of Brazil.
As for the Ciro Redondo mill, it will be built and operated by a joint venture between AZCUBA shareholder ZERUS, and the Havana Energy Company, from the UK. Installation and commissioning will be undertaken through a turnkey project led by Shanghai Electric, winner of the tender for this purpose.
Currently there are 200 bioelectrical plants in operation worldwide, of which the largest number, about 140, are located in Brazil. According to experts, this type of work is at the forefront of the current world sugar industry.